Fixed the build of ndt_2d with Eigen 3.3

[bouffa]

Fixes http://www.pcl-users.org/Compiling-PCL-1-8-with-visual-studio-2013-td4043387.html

[jspricke]

Hi Mourad, great to see you here :). Looking at Eigen, shouldn't it be rather PointT instead of double? On the other side, Real is the same, so +1 from me.

[bouffa]

Hi Jochen, thanks :)

According to Eigen::NumTraits< T > Class Template Reference , Literal should be a numeric type :

A typedef Literal giving the type to use for numeric literals such as "2" or "0.5". For instance, for std::complex, Literal is defined as U. Of course, this type must be fully compatible with T. In doubt, just use T here.

[LeonsID]

why not typedef PointT Literal; ?